Method for stably and controllably synthesizing silver nanowire under condition of not using organic solvent

Abstract

The invention relates to a silver nanowire preparation technology, and aims to provide a method for stably and controllably synthesizing a silver nanowire under the condition of not using an organic solvent. Comprising the following steps: mixing and stirring silver ions, a carbohydrate compound and a PVP (Polyvinyl Pyrrolidone) aqueous solution, continuously adding a chloride ion aqueous solution serving as a nucleating agent, mixing and stirring, transferring into a hydrothermal reaction kettle, and reacting under a heating condition to obtain a silver nanowire mother solution; and sediments in the silver nanowire mother liquor are separated and cleaned, and the silver nanowires with the length-diameter ratio being 800-845 are obtained. In the synthesis and purification process of the silver nanowire, water is used for replacing an alcohol or acetone solvent, so that the problem of insufficient environmental protection property in the existing method is solved; the process stability is improved by regulating and controlling the hydrothermal reaction process parameters; the microtopography of the silver nanowire is regulated and controlled by cooperatively regulating and controlling the dosage of the carbohydrate compound and the nucleating agent, the process repeatability is improved, the problem that in an existing polyhydric alcohol method, the product difference is large is solved, and finally stable and controllable synthesis of the silver nanowire is achieved.

Description

Technical Field

[0001] The present invention relates to a silver nanowire preparation technology, and in particular to a method for stably and controllably synthesizing silver nanowires without using an organic solvent. The method is a green silver nanowire synthesis method. Background Art

[0002] In recent years, indium tin oxide (ITO), with its high transparency and low resistivity, has become the most widely used material for transparent conductive electrodes. With the development of flexible electronic products such as wearable devices, smartphones, and sensors, higher requirements are being placed on the bending resistance of electrode materials. Due to the inherent brittleness of indium tin oxide (ITO), it is difficult to meet the needs of existing flexible electronic products. Silver nanowires (AgNWs) have advantages such as excellent nanoscale effects, electrical conductivity, bending resistance, and high transparency. These advantages make them not only the most promising material to replace traditional indium tin oxide (ITO), but also give them great application potential in the field of new flexible electronic products.

[0003] Common methods for synthesizing silver nanowires include template methods, solvothermal methods, and polyol methods. Patent publication number CN113714509B discloses a method for preparing silver nanowires by urea reduction. This method involves dissolving urea and silver nitrate in ethylene glycol, sonicating the mixture for a period of time, and then placing the mixture in an ice bath for later use. Polyvinyl pyrrolidone (PVP) is then dissolved in ethylene glycol, heated to 150-180°C and kept warm. The urea and silver nitrate mixture is then added dropwise to the PVP solution. After nitrogen is introduced, the mixture is allowed to stand and stir to react, ultimately yielding silver nanowires. This method uses ethylene glycol as both the solvent and the reducing agent, and the operation requires sonication, an ice bath, and nitrogen flow, making the process cumbersome and failing to meet environmental protection requirements. Patent publication number CN115519132A discloses a method for synthesizing high-aspect-ratio silver nanowires. This method involves dissolving a soluble silver salt, a first ion additive, a second ion additive, polyvinyl pyrrolidone, and a reducing agent in ethylene glycol. A hydrothermal reaction is performed to obtain a silver nanowire mother liquor. During the silver nanowire washing process, acetone is first added to the mother liquor. After removing the supernatant, the precipitate is dispersed with anhydrous ethanol. The silver nanowires are then centrifuged multiple times to obtain the silver nanowires. This method not only uses organic solvents such as ethylene glycol as both a solvent and a reducing agent, but also requires the use of a controlled chemical, acetone, during the washing process, making it difficult to meet environmental protection requirements. Furthermore, according to the patent's examples, under certain conditions, this method can synthesize silver nanowires with a length of approximately 100 μm and an average diameter of 71 nm. However, under other conditions, the synthesized silver nanowires are less than 50 μm in length, and under some conditions, the product is primarily larger micron- and submicron-sized silver particles. This indicates that the reaction products produced by this method exhibit significant variability, and the stability of the preparation process is poor.

[0004] Among the currently reported synthetic methods, the polyol method remains the most commonly used for silver nanowire synthesis. This method uses alcohols such as ethylene glycol and glycerol as solvents, relying on the high-temperature decomposition of polyols into aldehydes to provide a reductive catalyst for the synthesis of silver nanowires. While some research has reported that this method can synthesize silver nanowires with high aspect ratios, the use of organic solvents such as ethylene glycol makes it difficult to meet environmental protection requirements. Furthermore, some research reports indicate that the products synthesized using this method exhibit significant variability.

[0005] Therefore, developing a green and controllable synthesis method for silver nanowires is of great significance for the large-scale application of silver nanowires. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a method for stably and controllably synthesizing silver nanowires without using an organic solvent.

[0007] To solve the technical problem, the solution of the present invention is:

[0008] Provided is a method for stably and controllably synthesizing silver nanowires without using an organic solvent, comprising:

[0009] After mixing and stirring the silver ion aqueous solution, the saccharide compound aqueous solution and the polyvinyl pyrrolidone (PVP) aqueous solution, a chloride ion aqueous solution as a nucleating agent is added, and the mixture is mixed and stirred to obtain a reaction solution;

[0010] The reaction solution is transferred to a hydrothermal reactor and reacted under heating conditions to obtain a silver nanowire mother solution;

[0011] Separate and clean the sediment in the silver nanowire mother liquor to obtain silver nanowires with an aspect ratio of 800 to 845.

[0012] As a preferred embodiment of the present invention, the silver ion aqueous solution is a silver nitrate aqueous solution.

[0013] As a preferred embodiment of the present invention, the carbohydrate compound is glucose or maltose.

[0014] As a preferred embodiment of the present invention, the polyvinyl pyrrolidone (PVP) aqueous solution is obtained by adding PVP into water and stirring and dissolving it at 65° C.; the PVP model used is any one of K90, K30 or K60.

[0015] As a preferred embodiment of the present invention, the chloride ion aqueous solution is an aqueous solution of any one of sodium chloride, copper chloride and ferric chloride.

[0016] As a preferred embodiment of the present invention, when preparing each solution and reaction solution, the stirring speed is controlled to be 600-750 r / min.

[0017] As a preferred embodiment of the present invention, in the reaction solution, the molar ratio of silver ions: carbohydrate compound: polyvinyl pyrrolidone: chloride ions is 1:2-6:75:0.1-1.

[0018] As a preferred embodiment of the present invention, the reaction conditions in the hydrothermal reactor are: reaction temperature 150-160° C., reaction time 16-18 h, and the amount of reaction solution added is more than 80% of the reactor volume.

[0019] As a preferred embodiment of the present invention, the sediment is separated and cleaned by the following method: water is added to the silver nanowire mother liquor to dilute it, and the upper liquid is removed after centrifugation; the sediment is dispersed with the same volume of water and then centrifuged to remove the supernatant; the operation is repeated 4 to 5 times to finally obtain the silver nanowire product.

[0020] As a preferred embodiment of the present invention, the diameter of the silver nanowires is 49 to 57 nm, and the length is 40 to 50 μm.

[0021] Description of the invention principle:

[0022] The existing polyol method for synthesizing silver nanowires primarily uses alcohols such as ethylene glycol and glycerol as solvents. At high temperatures, these alcohols are reduced to aldehydes, providing reducing power to the reaction system and enabling the growth of silver nanowires. These alcohols serve as both solvents and reducing agents, thus reducing the production cost of silver nanowires to a certain extent. Furthermore, the polyol method is currently the most widely researched and mature method. Its simplicity and potential for large-scale application make it the most widely used method for silver nanowire synthesis. During the silver nanowire purification process, acetone can selectively dissolve polyvinylpyrrolidone that is not adsorbed on the silver nanowire surface, effectively separating the silver nanowires from byproducts such as nanoparticles. The sediment can then be washed repeatedly with ethanol to obtain high-purity silver nanowires. While the polyol method demonstrates promising potential for large-scale application, the preparation process requires the use of alcohols such as ethylene glycol and glycerol as solvents, and the purification and washing processes require large amounts of ethanol or acetone for dilution, making it difficult to meet environmental protection requirements. Furthermore, because the alcohol raw materials used in the polyol method offer strong reducing power at high temperatures, the resulting products are susceptible to variability due to the effects of reaction conditions, requiring precise control of reaction parameters to ensure product stability. Furthermore, in large-scale production, processing costs are often limited, often requiring the use of only industrial-grade polyol raw materials to effectively reduce production costs. This negatively impacts the preparation process due to factors such as the purity and impurities of the polyol raw materials, which can also lead to significant variability in the synthesized products, limiting the application of silver nanowires.

[0023] To address these issues, the present invention replaces the polyol solvent used in existing methods with water during silver nanowire synthesis and replaces alcohol or acetone solvents during silver nanowire purification, addressing the environmental shortcomings of existing methods. The introduction of environmentally friendly carbohydrate compounds provides reducing power to the system, ensuring smooth reaction progress. Furthermore, by synergistically controlling various hydrothermal reaction process parameters, the present invention improves method stability, overcoming the significant product variability found in existing polyol methods, ultimately achieving stable and controllable synthesis of silver nanowires.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention uses water to replace the polyol solvent in the existing method during the synthesis of silver nanowires, and uses water to replace alcohol or acetone solvents during the purification of silver nanowires, thereby improving the environmental protection problem of the existing method.

[0026] 2. This invention improves process stability by regulating hydrothermal reaction process parameters. By synergistically controlling the amount of carbohydrate compound and nucleating agent, the micromorphology of the silver nanowires is controlled, improving process repeatability. This overcomes the large product variability problem of existing polyol methods, ultimately achieving stable and controllable synthesis of silver nanowires. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 and Figure 2 This is a scanning electron microscope photograph of the silver nanowires prepared in Example 1.

[0028] Figure 3 and Figure 4 This is a scanning electron microscope photograph of the silver nanowires prepared in Example 2.

[0029] Figure 5 and Figure 6 This is a scanning electron microscope photograph of the silver nanowires prepared in Example 3.

[0030] Figure 7 This is a scanning electron microscope photograph of the reaction product of Comparative Example 1.

[0031] Figure 8 This is a scanning electron microscope photograph of the reaction product of Comparative Example 2.

[0032] Figure 9 This is a scanning electron microscope photograph of the reaction product of Comparative Example 3.

[0033] Figure 10 This is a scanning electron microscope photograph of the reaction product of Comparative Example 4.

[0034] Figure 11 This is a scanning electron microscope photograph of the reaction product of Comparative Example 5.

[0035] Figure 12 This is a scanning electron microscope photograph of the reaction product of Comparative Example 6. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0037] 1. Overview of the technical solution of the present invention

[0038] The present invention provides a method for stably and controllably synthesizing silver nanowires without using an organic solvent, comprising:

[0039] 1. Preparation of various solutions:

[0040] Silver ion aqueous solution, saccharide compound aqueous solution, polyvinylpyrrolidone (PVP) aqueous solution and chloride ion aqueous solution were prepared under stirring conditions respectively. Among them, the PVP solution was obtained by stirring and dissolving at 65°C, and the other solutions were obtained by stirring at room temperature.

[0041] As optional examples, the concentration of the silver ion aqueous solution is 10.19 g / L, and the solute is silver nitrate; the concentration of the sugar compound aqueous solution is 0.12 mol / L, and the solute is glucose or maltose; the solute in the chloride ion aqueous solution is any one of sodium chloride, copper chloride, and ferric chloride, and the concentration is 60 mmol / L; the concentration of the PVP aqueous solution is 55.5 g / L, and the model is any one of K90, K30 or K60. During preparation, PVP is added to water and stirred to dissolve at 65°C.

[0042] 2. Prepare reaction solution

[0043] An aqueous silver ion solution, an aqueous saccharide solution, and an aqueous polyvinylpyrrolidone (PVP) solution are added to a container and stirred for 10 minutes. An aqueous chloride ion solution, serving as a nucleating agent, is then added and stirred to obtain a reaction solution. The molar ratio of silver ion: saccharide: polyvinylpyrrolidone: chloride ion in the reaction solution is 1:2-6:75:0.1-1.

[0044] When preparing the above solutions and reaction solutions, control the stirring speed to 600-750 r / min.

[0045] 3. Thermal synthesis reaction

[0046] The reaction solution is transferred to a hydrothermal reactor and reacted at a temperature of 150-160° C. for 16-18 hours. The amount of reaction solution added is more than 80% of the volume of the reactor. After the reaction, a silver nanowire mother liquor is obtained.

[0047] Under laboratory conditions, a 25 mL hydrothermal reactor can be selected.

[0048] 4. Separate and clean the products

[0049] Add an appropriate amount of water to the silver nanowire mother liquor to dilute it, remove the upper liquid after centrifugation; disperse the sediment with the same volume of water and then centrifuge to remove the supernatant; repeat the operation 4 to 5 times to finally obtain the silver nanowire product.

[0050] As an optional example, the centrifugation speed is set at 3000 r / min and the centrifugation time is 5 minutes. The resulting silver nanowire product has a diameter of 49 to 57 nm, a length of 40 to 50 μm, and an aspect ratio of 800 to 845 after rounding.

[0051] 2. Examples and Comparative Examples

[0052] Example 1

[0053] The method for stably and controllably synthesizing silver nanowires without using an organic solvent is performed by the following steps:

[0054] (1) Weigh 0.15 g of silver nitrate and dissolve it in 15 mL of water. Stir the mixture at 600 rpm for 10 min at room temperature to obtain solution A.

[0055] (2) Weigh 0.11 g of sodium chloride and dissolve it in 30 mL of water. Stir the mixture at 600 rpm for 5 min to obtain solution B.

[0056] (3) Weigh 0.65 g of glucose and dissolve it in 30 mL of water. Stir the mixture at 600 rpm for 20 min at room temperature to obtain solution C.

[0057] (4) Weigh 14 g of polyvinylpyrrolidone K90 (Mw = 1300K) and dissolve it in 270 mL of water. Stir at 600 rpm at 65°C until the solution is homogeneous to obtain solution D.

[0058] (5) Measure 27 mL of solution D and place it in a 50 mL beaker. Place the beaker on a stirring platform and adjust the speed to 650 r / min. Then, add 3 mL of solution A and 3 mL of solution C to solution D at a volume ratio of solution D: solution A: solution C = 9:1:1, and mix and stir for 20 min.

[0059] (6) While keeping the rotation speed constant, 3 mL of solution B was added to the mixed solution obtained in step (5) at a volume ratio of solution D:solution B = 9:1, and the mixture was stirred for 20 minutes to prepare a reaction solution;

[0060] After conversion, the molar ratio of silver ions: carbohydrate compound: polyvinyl pyrrolidone: chloride ions in the reaction solution is 1:2:75:1.

[0061] (7) 20 mL of the reaction solution prepared in step (5) was measured and transferred to a 25 mL hydrothermal reactor. The reaction temperature was set to 160° C. and the reaction was carried out for 18 h to obtain a silver nanowire mother solution.

[0062] (8) Add 80 mL of water to the silver nanowire mother liquor at a volume ratio of silver nanowire mother liquor: water = 1:4, transfer the diluted silver nanowire mother liquor to a 500 mL centrifuge bottle, set the centrifugal speed to 3000 r / min, and the time for 5 min. After centrifugation, remove the upper liquid, disperse the sediment with 80 mL of water, and continue centrifugation;

[0063] (9) Repeat the cleaning operation of step (8) 4 to 5 times to obtain silver nanowires.

[0064] The micromorphology of the silver nanowires prepared by this method is as follows Figure 1 and Figure 2 As shown, the characteristic data of the nanowires were statistically analyzed using the particle size analysis software NanoMeasurer, and the results showed that the nanowire length was approximately 45 μm and the diameter was approximately 55 nm. Based on this, the aspect ratio was calculated to be 818. The characteristic data of the nanowires in the following examples and comparative examples were all obtained in this way.

[0065] Example 2

[0066] The method for stably and controllably synthesizing silver nanowires without using an organic solvent is performed by the following steps:

[0067] (1) Weigh 0.15 g of silver nitrate, dissolve it in 15 mL of water, and stir at 600 rpm for 10 min at room temperature to obtain solution A.

[0068] (2) Weigh 0.29 g of ferric chloride and dissolve it in 30 mL of water. Stir the mixture at 600 rpm for 5 min to obtain solution B.

[0069] (3) Weigh 0.65 g of glucose and dissolve it in 30 mL of water. Stir the mixture at 600 rpm for 20 min at room temperature to obtain solution C.

[0070] (4) Weigh 14 g of polyvinylpyrrolidone K90 (Mw = 1300K) and dissolve it in 270 mL of water. Stir at 650 rpm at 65°C until the solution is homogeneous to obtain solution D.

[0071] (5) Measure 27 mL of solution D and place it in a 50 mL beaker. Place the beaker on a stirring platform and adjust the speed to 750 r / min. Then, add 3 mL of solution A and 9 mL of solution C to solution D in a volume ratio of solution D: solution A: solution C = 9:1:3, and mix and stir for 20 min.

[0072] (6) While keeping the rotation speed constant, 0.3 mL of solution B was added to the mixed solution obtained in step (5) at a volume ratio of solution D:solution B = 9:0.1, and the mixture was stirred for 20 minutes to prepare a reaction solution;

[0073] After conversion, the molar ratio of silver ions: carbohydrate compound: polyvinyl pyrrolidone: chloride ions in the reaction solution is 1:6:75:0.3.

[0074] (7) 20 mL of the reaction solution prepared in step (5) was measured and transferred to a 25 mL hydrothermal reactor. The reaction temperature was set to 150° C. and the reaction was carried out for 18 h to obtain a silver nanowire mother solution.

[0075] (8) Add 80 mL of water to the silver nanowire mother liquor at a volume ratio of silver nanowire mother liquor: water = 1:4, transfer the diluted silver nanowire mother liquor to a 500 mL centrifuge bottle, set the centrifugal speed to 3000 r / min, and the time for 5 min. After centrifugation, remove the upper liquid, disperse the sediment with 80 mL of water, and continue centrifugation;

[0076] (9) Repeat the cleaning operation of step (8) 4 to 5 times to obtain silver nanowires.

[0077] The micromorphology of the silver nanowires prepared by this method is as follows Figure 3 and Figure 4 As shown, the nanowire length is about 48 μm, the diameter is about 57 nm, and the aspect ratio is 842.

[0078] Example 3

[0079] The method for stably and controllably synthesizing silver nanowires without using an organic solvent is performed by the following steps:

[0080] (1) Weigh 0.15 g of silver nitrate, dissolve it in 15 mL of water, and stir at 600 rpm for 10 min at room temperature to obtain solution A.

[0081] (2) Weigh 0.24 g of copper chloride and dissolve it in 30 mL of water. Stir the mixture at 600 rpm for 5 min to obtain solution B.

[0082] (3) Weigh 0.65 g of glucose and dissolve it in 30 mL of water. Stir the mixture at 600 rpm for 20 min at room temperature to obtain solution C.

[0083] (4) Weigh 14 g of polyvinylpyrrolidone K90 (Mw = 1300K) and dissolve it in 270 mL of water. Stir at 600 rpm at 65°C until the solution is homogeneous to obtain solution D.

[0084] (5) Measure 27 mL of solution D and place it in a 50 mL beaker. Place the beaker on a stirring platform and adjust the speed to 650 r / min. Then, add 3 mL of solution A and 6 mL of solution C to solution D in a volume ratio of solution D: solution A: solution C = 9:1:2, and mix and stir for 20 min.

[0085] (6) While keeping the rotation speed constant, 1.5 mL of solution B was added to the mixed solution obtained in step (5) at a volume ratio of solution D:solution B = 9:0.5, and the mixture was stirred for 20 minutes to prepare a reaction solution;

[0086] After conversion, the molar ratio of silver ions: carbohydrate compound: polyvinyl pyrrolidone: chloride ions in the reaction solution is 1:4:75:1.

[0087] (7) 20 mL of the reaction solution prepared in step (5) was measured and transferred to a 25 mL hydrothermal reactor. The reaction temperature was set to 160° C. and the reaction was carried out for 16 h to obtain a silver nanowire mother solution.

[0088] (8) Add 80 mL of water to the silver nanowire mother liquor at a volume ratio of silver nanowire mother liquor: water = 1:4, transfer the diluted silver nanowire mother liquor to a 500 mL centrifuge bottle, set the centrifugal speed to 3000 r / min, and the time for 5 min. After centrifugation, remove the upper liquid, disperse the sediment with 80 mL of water, and continue centrifugation;

[0089] (9) Repeat the cleaning operation of step (8) 4 to 5 times to obtain silver nanowires.

[0090] The micromorphology of the silver nanowires prepared by this method is as follows Figure 5 and Figure 6 As shown, the nanowire length is about 43 μm, the diameter is about 52 nm, and the aspect ratio is 826.

[0091] Example 4

[0092] The method for stably and controllably synthesizing silver nanowires without using an organic solvent is performed by the following steps:

[0093] (1) Weigh 0.15 g of silver nitrate, dissolve it in 15 mL of water, and stir at 600 rpm for 10 min at room temperature to obtain solution A.

[0094] (2) Weigh 0.11 g of sodium chloride and dissolve it in 30 mL of water. Stir the mixture at 600 rpm for 5 min to obtain solution B.

[0095] (3) Weigh 0.65 g of glucose and dissolve it in 30 mL of water. Stir the mixture at 600 rpm for 20 min at room temperature to obtain solution C.

[0096] (4) Weigh 14 g of polyvinylpyrrolidone K60 (Mw = 360K) and dissolve it in 270 mL of water. Stir at 600 rpm at 65°C until the solution is homogeneous to obtain solution D.

[0097] (5) Measure 27 mL of solution D and place it in a 50 mL beaker. Place the beaker on a stirring platform and adjust the speed to 650 r / min. Then, add 3 mL of solution A and 3 mL of solution C to solution D at a volume ratio of solution D: solution A: solution C = 9:1:1.5, and mix and stir for 20 min.

[0098] (6) While keeping the rotation speed constant, 3 mL of solution B was added to the mixed solution obtained in step (5) at a volume ratio of solution D:solution B = 9:0.1, and the mixture was stirred for 20 minutes to prepare a reaction solution;

[0099] After conversion, the molar ratio of silver ions: carbohydrate compound: polyvinyl pyrrolidone: chloride ions in the reaction solution is 1:3:75:0.1.

[0100] (7) 20 mL of the reaction solution prepared in step (5) was measured and transferred to a 25 mL hydrothermal reactor. The reaction temperature was set to 160° C. and the reaction was carried out for 18 h to obtain a silver nanowire mother solution.

[0101] (8) Add 80 mL of water to the silver nanowire mother liquor at a volume ratio of silver nanowire mother liquor: water = 1:4, transfer the diluted silver nanowire mother liquor to a 500 mL centrifuge bottle, set the centrifugal speed to 3000 r / min, and the time for 5 min. After centrifugation, remove the upper liquid, disperse the sediment with 80 mL of water, and continue centrifugation;

[0102] (9) Repeat the cleaning operation of step (8) 4 to 5 times to obtain silver nanowires.

[0103] The silver nanowires prepared by this method have a length of about 43 μm, a diameter of about 51 nm, and an aspect ratio of 843.

[0104] Example 5

[0105] In step (4) of Example 1, "weigh 14 g of polyvinyl pyrrolidone (Mw = 1300K)" was replaced with "weigh 14 g of polyvinyl pyrrolidone K30 (Mw = 40K)". After conversion, the molar ratio of silver ion: carbohydrate compound: polyvinyl pyrrolidone: chloride ion in the reaction solution was 1:2:75:1. The rest of the process was the same as in Example 1.

[0106] The synthesized nanowires have a length of about 41 μm, a diameter of about 49 nm, and an aspect ratio of 838.

[0107] Example 6

[0108] In step (3) of Example 1, "0.65 g of glucose dissolved in 30 mL of water" was replaced with "2.26 g of maltose dissolved in 30 mL of water". After conversion, the molar ratio of silver ion: carbohydrate compound: polyvinyl pyrrolidone: chloride ion in the reaction solution was 1:3.7:75:1. The rest of the process was the same as in Example 1.

[0109] The synthesized nanowires have a length of about 45 μm, a diameter of about 56 nm, and an aspect ratio of 804.

[0110] Example 7

[0111] In step (7) of Example 1, "the reaction temperature was set to 160°C and the reaction was carried out for 18 hours" was replaced with "the reaction temperature was set to 155°C and the reaction was carried out for 17 hours". After conversion, the molar ratio of silver ion: carbohydrate compound: polyvinyl pyrrolidone: chloride ion in the reaction solution was 1:2:75:1. The rest of the process was the same as in Example 1.

[0112] The synthesized nanowires have a length of about 42 μm, a diameter of about 51 nm, and an aspect ratio of 823.

[0113] Comparative Example 1

[0114] The reaction temperature was 140°C, except that the reaction temperature was 160°C in step (6) of Example 1 was replaced by the reaction temperature of 140°C. The rest of the reaction was the same as in Example 1. The results were as follows: Figure 7 As shown, particles and some short rods are formed after the reaction.

[0115] Comparative Example 2

[0116] The ratio of "solution D: solution A: solution C = 9:1:1" in step (5) of Example 1 was adjusted to "solution D: solution A: solution C = 10:1:1". The reaction product was as follows: Figure 8 As shown, the products are mainly nanorods and particles.

[0117] Comparative Example 3

[0118] The ratio of solution D: solution B = 9:1 in step (6) of Example 1 was adjusted to solution D: solution B = 9:2. The reaction product was as follows. Figure 9 As shown, the products are mainly nanowires and submicron particles, and the diameter of some nanowires is coarsened.

[0119] Comparative Example 4

[0120] The ratio of "solution D: solution A: solution C = 9:1:1" in step (5) of Example 1 was adjusted to "solution D: solution A: solution C = 9:1:3". The reaction product was as follows: Figure 10 As shown in the figure, the nanowire diameter is obviously coarsened.

[0121] Comparative Example 5

[0122] Silver nanowires were prepared according to the method reported in the literature (DOI 10.1007 / s12274-016-1049-2). Figure 11 As shown, the products prepared by this method are mainly particles and a small amount of nanowires.

[0123] Comparative Example 6

[0124] Silver nanowires were prepared according to the method reported in the literature (DOI 10.1038 / s41598-024-53286-8). Figure 12 As shown, the products prepared by this method are short rods and nanoparticles.

[0125] The final product morphology and analytical data from the above examples and comparative examples demonstrate that each of the present invention's examples produced silver nanowire products with similar morphologies, with comparable length, diameter, and aspect ratio. This demonstrates that the present invention, through the coordinated regulation of the amounts of carbohydrate compound and nucleating agent, not only modulates the micromorphology of the silver nanowires but also further improves process reproducibility. This overcomes the significant variability in product morphology associated with the prior art polyol process, ultimately achieving stable and controllable synthesis of silver nanowires.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for stably and controllably synthesizing silver nanowires without using an organic solvent, characterized in that: include: After mixing and stirring the silver ion aqueous solution, the saccharide compound aqueous solution and the polyvinyl pyrrolidone (PVP) aqueous solution, a chloride ion aqueous solution as a nucleating agent is added, and the mixture is mixed and stirred to obtain a reaction solution; The reaction solution is transferred to a hydrothermal reactor and reacted under heating conditions to obtain a silver nanowire mother solution; Separate and clean the sediment in the silver nanowire mother liquor to obtain silver nanowires with an aspect ratio of 800 to 845.

2. The method according to claim 1, characterized in that The silver ion aqueous solution is a silver nitrate aqueous solution.

3. The method according to claim 1, characterized in that The sugar compound is glucose or maltose.

4. The method according to claim 1, wherein The polyvinyl pyrrolidone (PVP) aqueous solution is obtained by adding PVP into water and stirring and dissolving it at 65° C.; the PVP model used is any one of K90, K30 or K60.

5. The method according to claim 1, wherein The chloride ion aqueous solution is an aqueous solution of any one of sodium chloride, copper chloride and ferric chloride.

6. The method according to claim 1, wherein When preparing each solution and reaction solution, control the stirring speed to 600-750 r / min.

7. The method according to claim 1, characterized in that In the reaction solution, the molar ratio of silver ions: sugar compound: polyvinyl pyrrolidone: chloride ions is 1:2-6:75:0.1-1.

8. The method according to claim 1, characterized in that The reaction conditions in the hydrothermal reactor are: reaction temperature 150-160° C., reaction time 16-18 hours, and the amount of reaction solution added is more than 80% of the reactor volume.

9. The method according to claim 1, characterized in that The sediment is separated and cleaned by the following method: water is added to the silver nanowire mother liquor to dilute it, and the upper liquid is removed after centrifugation; the sediment is dispersed with the same volume of water and then centrifuged to remove the supernatant; the operation is repeated 4 to 5 times to finally obtain the silver nanowire product.

10. The method according to any one of claims 1 to 9, characterized in that The diameter of the silver nanowire is 49-57 nm, and the length is 40-50 μm.

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